Bimolekulare Radikalbildung durch H‐Transfer, 2. H‐Transferreaktionen mit Phenalen

Bimolecular Formation of Radicals by H‐Transfer, 2[1]. – H‐Transfer Reactions of Phenalene The uncatalysed H transfer from phenalane (7) to α1‐methyl‐styrene (2) and the selfreaction (d) of phenalene (7) are quantitative transformations in the presence of an excess of 9,10‐dihydroanthracene (1) (DHA) in diphenyl ether at 200–250°C. In this system phenalene (7) is consumed only in reaction (d) because the phenalenyl radicals (9) are captured by DHA (1) to give phenalene (7) and 9,10‐dihydroanthryl radicals (3). The latter disproportionate rapidly. Accordingly, phenalene (7) acts as a catalyst for the hydrogenation of α1‐methylstyrene (2) by DHA (1). The activation parameters of the two reactions (e) and (d) were obtained from kinetic experiments between 200–250°C. They allow the determination of the CH bond enthalpy δHdiss of phenalene (7) (65.3 kcal mol–1) at the methylene position.